This invention is directed to a sizing composition and sized glass fibers produced therefrom that have a reduced tendency to form gumming deposits.
More particularly, the present invention is directed to a sizing composition and sized glass fibers produced therefrom that have a reduced tendency to form gumming deposits on fabrication machinery at high relative humidities.
Glass fibers in the form of strands are made from a multitude of fine glass fibers which are formed by being drawn at a high rate of speed from molten glass streams flowing from small openings in a bushing. Chemical sizing compositions are applied to the fibers during their formation to protect the fibers from abrading each other when they are gathered together into a strand and when the strand is further processed. Sizing compositions typically contain film-formers or binders, lubricants, coupling agents, and possible other additives like flexibilizing agents, wetting agents, stabilizing agents, plasticizers and emulsifying agents and the like. When the glass fibers are to be used in textile application, for example, in weaving of fabrics, and used as reinforcement for tapes such as carton ceiling tapes and box corner tapes, the sizing composition generally contains one or more starch film-formers or binders and one or more lubricants along with such additives as wetting agents, flexibilizing agents, emulsifiers and the like.
In processing glass fiber strands and producing many of the glass fiber products for textile application the glass fibers in the form of strands must pass through processing machinery such as guide bars and other orientation devices. For example, in the production of glass fiber reinforced tape, the glass fiber strands are oriented by meir bar for proper alignment before coming in contact with the tape material. Manufacturers of glass fiber reinforced material have encountered difficulty in producing the glass fiber reinforcement under high relative humidity conditions. Under these conditions, the current sizing compositions used on glass fibers to protect the fibers, produce sized glass fibers that have a tendency to leave gumming deposits on processing machinery such as guide bars or orientation devices like the meir bar.
These current sizing compositions contain one or more starches or a mixture of starches such as non-crosslinked cationic starches, derivatized starches, high amylose containing starches, low amylose containing starches, hydrolyzed starches such as dextrinized corn starch along with lubricants such as vegetable oil, cationic lubricants, solid and emulsified waxes and the like. In addition, such additives as cationic wetting agents, emulsifying agents, film-formers such as gelatin and polyvinyl alcohol may be added to a starch such as fully or partially dextrinized starch and a lubricant such as hydrogenated vegetable oil. Also, since there is a long drying period during which the wet starch and oil deposit on the glass may act as a base upon which fungus can grow, there is usually included in the sizing composition a small amount of fungicide and possibly a disinfectant. The amount of forming size deposited on the glass fiber is usually about 0.7 to about 2 percent by weight based on the weight of the glass.
The proportions of starch, oil and other additives and types of starch, oil and other additives in the sizing compositions have been varied to suit various requirements.
In U.S. Pat. No. 3,227,192 (Griffiths) a sized glass fabric and method are disclosed wherein the aqueous sizing composition contains as the binder ingredient an amylose containing starch mixture, having a amylose content of about 35 to 45 percent by weight based on the total starch content. The mixture is formed by mixing approximately equal portions of a high amylose starch fraction and a low amylose starch fraction wherein the remainder of the high and low amylose starch fraction is comprised of amylopectin. The high amylose fraction can constitute from about 45 to 55 percent by weight based on a total starch content of the starch mixture while the low amylose content starch fraction constitutes from 45 to 55 percent by weight of the mixture. If the high amylose component is employed in an amount significantly in excess of 55 percent by weight it becomes increasingly difficult to mix (blend) the two starch components especially in an aqueous medium and the viscosity characteristics are deleteriously affected and the burn-off (volatalization) of the binder becomes more difficult and expensive.
In U.S. Pat. No. 3,615,311 (Ignatius) a starch sizing composition is disclosed for coating glass fibers which has greatly improved drying properties. The starch sizing composition has a relatively narrow range of a non-crosslinked cationic starch which is made cationic by attaching a nitrogen or phospherous with an unshared pair of electrons thereon to a natural starch molecule and an underivatized starch that is preferably high in amylose having a portion of the granules that are incompletely burst.
Also, in U.S. Pat. No. 3,869,308 (Graham) a method of producing an improved sized glass fiber strand suitable for plastisol coating is disclosed. The starch-based sizing composition used to coat the glass fiber strands contains a starch, the salt of a polyamino functional polyamide resin and a carboxylic acid, a wax, and fatty triglyceride. Also, in U.S. Pat. No. 4,066,106 (Graham) a sizing composition for textile glass fibers is disclosed that has a starch, a textile softener, a lubricant and 100 to 150 percent by weight of combined non-ionic wetting agents based on the weight of said lubricant. U.S. Pat. Nos. 3,664,855 and 3,928,666 (Morrison et al) teach the partial cooking of etherified starch or esterified starch, respectively, where the starch has a unique coaction with emulsified particles of solid unctuous materials such as fat, wax, and gelled oil. The sizing composition of Morrison contains in addition to the aforementioned components, a cationic lubricant and emulsifying agent such as an emulsifier for the non-ionic lubricant (alkyl phenoxypolyethyleneoxyethanol) and an emulsifier such as sorbitan monostearate and can also contain a starch diluent and secondary film-former and non-ionic oil.
It was recently suggested in a copending, commonly assigned, patent application to produce a sized glass fiber strand having a reduced tendency to form gumming deposits by using a sizing composition having about 50 to about 65 percent by weight of the sizing composition, based on the non-aqueous components, of a cross-linked starch which has been partially cooked to within about 50 percent of complete cooking along with a salt of a polyamino functional polyamide resin, a wax, and fatty triglyceride. It was found in using this recently developed sizing composition that processing problems of binder cook-out on heating coils, and high binder usage, and soft shouldered forming packages were troublesome.
It is an object of the present invention to provide a sizing composition that yields sized glass fibers having a reduced tendency to form gumming deposits while presenting few, if any, processing problems.
It is an additional object of the invention to provide a sizing composition and sized glass fibers made therefrom, wherein the sized glass fibers have a reduced tendency to form gumming deposits and are produced with the sizing composition while minimizing binder cook-out, high binder usage, or the production of soft shouldered forming packages.